Head-up display device

ABSTRACT

The head-up display device includes a display element that emits image light and a virtual image optical system. The virtual image optical system includes a lens unit and a free curved surface mirror disposed along the emission direction of the image light in this order from a position close to the display element. The display element is disposed with a tilting attitude with respect to the optical axis of the lens unit with an end on the housing aperture side in an emission surface being close to an incidence surface in the lens unit and with an end on the opposite side of the housing aperture in an emission surface being apart from an incidence surface in the lens unit. The lens unit has an optical characteristic of optically enlarging an optical path length difference according to a virtual image distance difference.

TECHNICAL FIELD

The present invention relates to a head-up display device.

BACKGROUND ART

In a vehicle such as an automobile for example, information such as avehicle speed and an engine speed is normally displayed on an instrumentpanel inside a dashboard. Also, the screen of car navigation and thelike is displayed on a display incorporated in the dashboard orinstalled on the dashboard. Since it is required for a driver to largelymove the visual line when the driver visually contacts the information,head-up display devices are known a technology for reducing the movingamount of the visual line, whereas such device (hereinafter, beingdescribed as “HUD”) projects and displays information such as a vehiclespeed and information such as an instruction related to car navigationon the windshield and the like.

As a technology related to a HUD, such HUD for example has beendisclosed in Patent Literature 1 that “The data for head-up displaydisplayed image from an operation parameter detection device is input toa display control circuit. A display body is disposed generallyhorizontally with display boards being arranged at vertical intervalsfrom each other, and the display boards are transparent excluding theirdisplay areas. The display control circuit controls each display boardto display the displayed image on the plural display boards. A backlightlight source is arranged below the display boards, the light of thebacklight light source reaches the upper display board, and the emissionlight from each display board passes through a louver and is made toincident on a combiner. By switching the display board displayinginformation, the distance from the driver's eye position to the positionwhere the virtual image is displayed can be made variable without usinga movable mechanism (excerption of the abstract)”.

CITATION LIST Patent Literature

-   -   PATENT LITERATURE 1: JP-A No. 2004-168230

SUMMARY OF INVENTION Technical Problem

In the HUD described in Patent Literature 1, plural display boards aredisposed along the emission direction of the emission light. Therefore,in order to prevent the displayed image displayed on a display boarddisposed on the backlight light source side from being blocked by thedisplay board disposed on the opposite side of the backlight lightsource side namely the louver side, each display board is provided witha display area and a transparent area. Also, three kinds of the displayboards where the positions of the transparent area and the display areaare shifted so that the display areas do not overlap each other in theemission direction are used as one set, it is required to adjust anddispose the positions of the transparent area and the display area ofthe three display boards along the traveling direction of the emissionlight, and therefore there is a fact that manufacturing of the HUDincurs time and effort.

Therefore, the object of the present invention is to provide a head-updisplay device that improves the time and effort incurred inmanufacturing a HUD that displays virtual images having differentvirtual image distances.

Solution to Problem

In order to solve the problem described above, the present invention hasconfigurations as described in the claims. As an aspect of the presentinvention, the present invention is a head-up display device displayinga virtual image for a driver, including an image display device thatincludes a light source and a display element and forms an image on thedisplay element, a virtual image optical system that displays a virtualimage related to the image in front of a vehicle by reflecting imagelight including the image emitted from the image display device by aprojection target member, and a housing that stores the virtual imageoptical system, in which the housing includes an aperture through whichthe image light is emitted, the virtual image optical system includes alens unit and a free curved surface mirror disposed along the emissiondirection of the image light in this order from a position close to anemission surface of the image light in the display element, the displayelement is disposed with a tilting attitude with respect to an opticalaxis of the lens unit with an end on the aperture side in the emissionsurface being made close to an incident surface in the lens unit andwith an end on the opposite side of the aperture in the emission surfacebeing made apart from the incident surface in the lens unit, and thelens unit has an optical characteristic of optically enlarging anoptical path length difference that is the difference between a firstoptical path length from the end on the aperture side to the incidentsurface of the lens unit and a second optical path length from the endon the opposite side of the aperture side to the incident surface of thelens unit.

Advantageous Effect of Invention

According to the present invention, it is possible to provide a head-updisplay device that improves the time and effort incurred inmanufacturing a HUD that displays virtual images having differentvirtual image distances. Also, objects, configurations, and effectsother than those described above will be clarified in embodimentsdescribed below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration drawing of a head-up display deviceaccording to the present embodiment.

FIG. 2A is a perspective view that shows an external appearance around ahousing of an HUD.

FIG. 2B is a perspective view that shows a state of disintegrating theHUD shown in FIG. 2A into each component.

FIG. 3 is a drawing that shows a general outline on an example of animplementation of a image display device according to the presentembodiment.

FIG. 4 is a drawing that shows the tilting attitude of a displayelement, the optical path length difference and the virtual imagedistance difference.

FIG. 5A is a drawing that shows an example of a lens unit used in thepresent embodiment.

FIG. 5B is a drawing that shows an example of a lens unit used in thepresent embodiment.

FIG. 6A is a perspective view that shows an example of an externalappearance around an exterior housing of the HUD.

FIG. 6B is a perspective view that shows a state of disintegrating theHUD shown in FIG. 6A into each component.

FIG. 7A is a perspective view that shows an example of an externalappearance of a self-luminous film irradiation device according to asecond embodiment.

FIG. 7B is a perspective view that shows a state of disintegrating eachcomponent of the self-luminous film irradiation device according to thesecond embodiment.

FIG. 8 is a drawing that shows the virtual image distance difference inthe second embodiment.

FIG. 9A is a perspective view that shows an example of an externalappearance around an exterior housing of a HUD.

FIG. 9B is a perspective view that shows a state of disintegrating theHUD shown in FIG. 9A into each component.

FIG. 10A is a perspective view that shows an example of an externalappearance of a virtual image distance variable mechanism.

FIG. 10B is a perspective view that shows a state of disintegrating eachcomponent of the virtual image distance variable mechanism.

FIG. 11 is a flowchart that shows a flow of an optical path switchingprocess executed by a controller.

FIG. 12A is a drawing that shows a state where the first optical pathhas been formed.

FIG. 12B is a drawing that shows a state where the second optical pathhas been formed.

FIG. 12C is a drawing that shows a disposal state of each mirror in asunlight blocking state.

FIG. 13A is a drawing that shows a functional block example of thecontroller.

FIG. 13B is a drawing that shows a functional block example of thecontroller.

FIG. 14 is a drawing that shows a hardware configuration example of thecontroller.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained indetail based on the drawings. Also, in all drawings for explaining theembodiments, a same member is marked with a same reference sign inprinciple, and repeated explanation for it will be omitted. Meanwhile,there is a case that a portion explained with a reference sign in adrawing is referred to with the same reference sign in explanation ofanother drawing although repeated illustration thereof is omitted.Further, although each embodiment shown below is explained exemplifyinga case of installing a head-up display device (HUD) on a vehicle such asan automobile, the present invention is also applicable to otherconveyances such as a train and an aircraft etc. Furthermore, thepresent invention is also applicable to a HUD for uses other than aconveyance.

First Embodiment

In a first embodiment an image display device including a displayelement such as an LCD panel and a lens unit are used, the displayelement is held at a tilting attitude, and virtual images havingdifferent virtual image distances are displayed utilizing therelationship between the magnification of the lens unit and the disposalposition of the display element and the lens unit. Hereinafter,explanation will be made referring to the drawings.

FIG. 1 is a schematic configuration drawing of a head-up display deviceaccording to the present embodiment. A HUD device 1 reflects image lightincluding an image displayed by an image display device 30 disposedwithin an exterior housing 50 by a free curved surface mirror 41, andprojects the image light on a windshield 3 of a vehicle 2. The imagelight projected on the windshield 3 is made to be incident to the eyesof a driver 5, and the driver thereby visually contacts a virtual image80 in front of the vehicle 2. The free curved surface mirror 41 rotatesby a mirror drive section 42. Thereby, the free curved surface mirror 41changes the angle at which the image light is reflected towards thewindshield 3.

Here, a projection target member is not limited to the windshield 3, butcan be another member such as a combiner as far as it is a member towhich the image light is projected. Also, in the present embodiment, asthe image display device 30, a projector having a backlight and an LCD(Liquid Crystal Display) 30 are used. A VFD (Vacuum Fluorescent Display;used in the second embodiment described below) of a self-luminous typeand the like may be applicable. A projection device displaying an imageon a screen may be also applicable. Such screen may be configured forexample by a micro lens array in which micro lenses aretwo-dimensionally arranged.

Between the free curved surface mirror 41 and the image display device30, a lens unit 43 is provided which is for adjusting the opticaldistance between the free curved surface mirror 41 and the image displaydevice 30. Therefore, the lens unit 43 and the free curved surfacemirror 41 are disposed in order of proximity from the image displaydevice 30 side along the emission direction of the image light from theimage display device 30 to form a virtual image optical system, and areaccommodated inside the exterior housing 50.

FIG. 2A and FIG. 2B are drawings that show a general layout on anexample of an implementation of a head-up display device that is anembodiment of the present invention. FIG. 2A is a perspective view thatshows an example of an external appearance around the exterior housing50 of the HUD 1. Also, FIG. 2B is a perspective view that shows the HUD1 shown in FIG. 2A disassembled into its components.

As shown in FIG. 2B, the HUD 1 has such configuration that an opticalcomponent holding member 53 is accommodated in an exterior case 54, andthe upper part is covered by an exterior lid section 51. Each member ofthe exterior case 54 and the exterior lid section 51 configures theexterior housing 50 in the HUD 1 shown in FIG. 1. Also, the imagedisplay device 30 is attached to an aperture of the exterior case 54.

The exterior lid section 51 has an aperture for emitting the image lighttowards the windshield 3, and the aperture is covered by a glare trap52.

The optical component holding member 53 is a member that holds the freecurved surface mirror 41 and the lens unit 43 in the HUD 1 shown in FIG.1.

To the exterior case 54, other components such as a main base plate 70and the mirror drive section 42 may be attached, wherein the main baseplate 70 being mounted with a control section that controls operation ofan LED light source 31 a and a backlight and the like described belowand the mirror drive section 42 including a motor and the like forchanging the inclination angle of the free curved surface mirror 41. Inthe present embodiment, an attaching/detaching mechanism such as a screwhole and the like allowing attaching/detaching of the image displaydevice 30 and an aperture and the like for entering of the image lightare further formed.

In the present embodiment, the image display device 30 is modularized,and is configured to allow it to be integrally attached/detached to theexterior case 54 by screws and the like. Thereby, for example, only theimage display device 30 can be replaced without detaching ordisassembling the HUD 1 itself. Also, by attaching the image displaydevice 30 outside the exterior housing 50 of the HUD 1, the heatradiation performance can be improved and an effect of reducing failureand deterioration due to heat can also be obtained.

FIG. 3 is a drawing that schematically shows an example of animplementation of the image display device 30. Here, image a perspectiveview shows a state in which the modularized image display device 30 isdisassembled into its components. The image display device 30 displaysan image by that a display element 33 such as an LCD panel modulateslight from the backlight based on an image signal inputted from the mainbase plate 70 through a flexible cable 34. The image having beendisplayed is outputted to a virtual image optical system (the lens unit43 and the free curved surface mirror 41 in FIG. 2 in the presentembodiment) through the aperture of the exterior case 54 in FIG. 2, anda virtual image is generated which the driver 5 can visually contact.

For a light source element in the backlight, for example, a relativelyinexpensive and highly reliable LED (Light Emitting Diode) light source31 a is used as a solid-state light source. The LED light source 31 a isof a surface emission type in order to ensure a high output. In theexample of FIG. 3, the LED light source 31 a is mounted as an LED baseplate. In this case, for example, the utilization efficiency of thedivergent light is improved using such technical devisal as describedbelow.

The luminous efficiency of the LED with respect to input power isapproximately 20 to 30% which differs according to the emission color,and the rest is converted to heat. Therefore, in frame 35 to which theLED light source 31 a is attached, fins (heat sink 31 b) for heatradiation formed of an element with high thermal conductivity (a metalelement such as an aluminum element for example) are arranged todissipate the heat to the outside.

In order to efficiently guide the divergent light from the LED lightsource 31 a to the display element 33, in the example of FIG. 3, a lightguide body 32 b and a diffusion plate 32 c are used. In this case, inorder to prevent attachment of dust etc., it is preferable to cover thewhole light guide body 32 b, the diffusion plate 32 c, the displayelement 33 and the like by the exterior members 36 a, 36 b for exampleand to modularize as the image display device 30.

Also, in the example of FIG. 3, in order to take in the divergent lightfrom the LED light source 31 a and to make the divergent light parallellight, a plurality of light funnels 32 a formed of a collimate lens orthe like provided. An aperture that takes in the divergent light fromthe LED light source 31 a in each light funnel 32 a is, for example, aflat surface and is optically connected to the LED light source 31 awith a medium being inserted between the LED light source 31 a, or has aconvex shape with a light collecting effect. Thereby, the divergentlight is made into as much as parallel light as possible, and theincident angle of the light entering the interface of the light funnel32 a is reduced. As a result, because the diversion angle after passingthrough the light funnel 32 a can be reduced, the light of the lightsource heading to the display element 33 after being reflected by thelight guide body 32 b can be easily controlled.

In order to further improve the utilization efficiency of the divergentlight from the LED light source 31 a, polarization conversion using aPBS (Polarizing Beam Splitter) is executed in the joining part of thelight funnel 32 a and the light guide body 32 b, and the divergent lightis converted to a desired polarization direction. Thereby, theefficiency of the incident light to the display element 33 can beimproved. As described above, when the polarization direction of thelight of the light source is aligned, it is preferable to use materialwith less birefringence as the material of the light guide body 32 b.Thereby, when the divergent light passes through the display element 33while the polarization direction is rotated, for example, it is possibleto suppress occurrence of problems such as coloration at the time ofdisplaying black color.

FIG. 4 is a drawing that shows the tilting attitude of the displayelement, the optical path length difference, and the virtual imagedistance difference. As shown in FIG. 4, an emission surface 33 a of theimage light in the display element 33 of the image display device 30 isdisposed with a tilting attitude P₁ of tilting from a reference positionP₀ in such direction that the upper end of the emission surface 33 acomes closer to the lens unit 43 side and the lower end comes apart fromthe lens unit 43 side, the position where the emission surface 33 abecomes perpendicular to an optical axis of the lens unit 43 being madeto be the reference position P₀. As a result, when the depression angleof the emission surface 33 a with respect to the reference position P₀is made θ, the optical path length difference ΔL between a first opticalpath length L1 from the upper end of the emission surface 33 a(equivalent to an end on the aperture side of the exterior lid section51 in the emission surface 33 a) to the lens unit 43 and a secondoptical path length L2 from the lower end (equivalent to an end on theopposite side of the aperture of the exterior lid section 51 in theemission surface 33 a) to the lens unit 43 can be expressed by formula(1) below.

$\begin{matrix}\left\lbrack {{formula}\mspace{11mu} 1} \right\rbrack & \; \\\begin{matrix}{{\Delta\; L} = {{L\; 2} - {L\; 1}}} \\\left. {= {\left\lbrack \left( {{L1} + {\left( {\alpha/2} \right)\sin\;\theta}} \right) \right\rbrack - \left\lbrack {{L\; 1} - {\left( {\alpha/2} \right)\sin\;\theta}} \right)}} \right\rbrack \\{= {{\alpha sin}\;\theta}}\end{matrix} & (1)\end{matrix}$

where α is the length of the left side or right side of the emissionsurface 33 a.

Meanwhile, the first optical path length L1 from the lens unit 43 to theupper end of the emission surface 33 a and the second optical pathlength L2 from the lens unit 43 to the lower end of the emission surface33 a are shorter than the focal point distance of the lens unit 43. Inthat case, the upper end and the lower end of the virtual image 80 aredisplayed at respective positions of a first virtual image distance D1and a second virtual image distance D2 from the lens unit 43 accordingto formulas (2) and (3) with a magnification m=D1/L1=D2/L2. Also, themagnification m is equal to the size m of the virtual image 80 when thesize of the display image on the emission surface 33 a is made 1.

[formula 2]

1/L1+1/D1=1/f  (2)

[formula 3]

1/L2+1/D2=1/f  (3)

From formula (2) and formula (3),

$\begin{matrix}\left\lbrack {{formula}\mspace{14mu} 4} \right\rbrack & \; \\{{{{{1/L}\; 1} + {{1/D}1}} = {{{1/L}2} + {{1/D}2}}}{{{{1/D}1} - {{1/D}2}} = {{{1/L}2} - {{1/L}1}}}{{\left( {{D2} - {D1}} \right)/\left( {D\;{1 \cdot D}\; 2} \right)} = {\left( {{L\; 2} - {L\; 1}} \right)/\left( {L\;{1 \cdot L}\; 2} \right)}}\begin{matrix}{{\Delta\; D} = {\Delta\;{{L\left( {D\;{1 \cdot D}\; 2} \right)}/\left( {L\;{1 \cdot L}\; 2} \right)}}} \\{= {\Delta\;{L \cdot m^{2}}}}\end{matrix}} & (4)\end{matrix}$

When the virtual image distance difference ΔD between the upper end andthe lower end of the virtual image 80 is given as a desired value informula (4), because ΔL is a value determined mechanically from thestructure of the HUD 1, the optical characteristic of the lens unit 43only has to include the magnification m that satisfies (4). Also, bydisposing the display element 33 at a position shorter than the focalpoint distance fo of the lens unit 43, the virtual image 80 having thevirtual image distance difference ΔD can be displayed. Also, in theactual implementation, even when the virtual image distance differenceΔD is not strictly an equal value to formula (4), the virtual imagedistance difference ΔD only has to be in an allowable range where thevirtual image distance difference ΔD can be deemed to be equal to theoptical path length difference enlarged by the lens unit 43.

FIG. 5A and FIG. 5B are drawings that show an example of the lens unitused in the present embodiment. The lens unit 43 may be a single lens,and may be a so-called set lens that is obtained by combining aplurality of lenses. In general, when a lens is not used, a trapezoidaldistortion occurs in the image of the HUD because of the inclination andthe like of the windshield 3. Therefore, by tilting the display element33 so that the trapezoidal distortion generated in the windshield 3becomes a rectangle, the distance from the upper end of the displayelement 33 to the windshield 3 and the distance from the lower end ofthe display element 33 to the windshield 3 are changed, and thereby,improvement of correction of the trapezoidal distortion caused by theinclination of the windshield 3 can be effected to some extent. However,when the display element 33 is tilted too much, deterioration of theimage quality caused by deterioration of the contrast of the image etc.occurs, and therefore there is a limit in the distortion correctioneffect obtained by tilting of the display element 33.

Meanwhile, in the present embodiment, by incorporating a distortioncorrection lens to the lens unit 43 having a magnification that achievesa desired virtual image distance difference, a virtual image isdisplayed with the desired virtual image distance difference whileimproving the correction effect of the trapezoidal distortion. As thelens unit 43 used in the present embodiment, such distortion correctionlens having a free curved surface shape whose surface shape is definedas a function of the absolute coordinates (x, y) from the optical axisis used. The free curved surface shape is expressed by the followingformula (5).

$\begin{matrix}{\mspace{79mu}\left\lbrack {{formula}\mspace{14mu} 5} \right\rbrack} & \; \\{{Z = {\frac{c \cdot \left( {x^{2} + y^{2}} \right)}{1 + \sqrt{1 - {\left( {1 + K} \right){c^{2} \cdot \left( {x^{2} + y^{2}} \right)}}}} + {\sum{\sum\left( {C{j\left( {m,n} \right)} \times x^{m} \times y^{n}} \right)}}}}\mspace{79mu}{j = {{\left\lbrack {\left( {m + n} \right)^{2} + m + {3n}} \right\rbrack/2} + 1.}}} & (5)\end{matrix}$

By using the distortion correction lens described above, the opticalpath length difference structurally determined from the emission surface33 a of the display element 33 to the incident surface of the lens unit43 is optically corrected to the optical path length differencecorresponding to the virtual image distance difference while reducingdeterioration of the image forming performance of the virtual imagewhich is caused by a difference in the curvature radius of thewindshield 3.

According to the present embodiment, it is possible to provide a HUDthat holds the display element at a tilting attitude and displaysvirtual images with different virtual image distances based on therelationship of the magnification of the lens unit and the disposalposition of the display element and the lens unit. In thisconfiguration, because the display element and the lens unit can beappropriately as general-purpose products, procurement of componentsbecomes easier compared to a case of using specialized components, andreduction of the manufacturing cost can be expected.

Second Embodiment

In the second embodiment, instead of the image display device of thefirst embodiment, a self-luminous film irradiation device is used whichincludes a plurality of projectors that irradiate light having differentfrequencies and a plurality of self-luminous films that react todifferent frequencies, and respective self-luminous films are disposedat intervals along the emission direction of irradiation lightirradiated from the projector. Thereby, in each of the emission lighthaving different frequencies, an optical path length differenceequivalent to an optical path length according to the interval betweenthe self-luminous films occurs. Therefore, in the second embodiment,virtual images having different virtual image distance differences aredisplayed using this optical path length difference. Hereinafter,explanation will be made referring to the drawings.

FIG. 6A is a perspective view that shows an example of an externalappearance around the exterior housing 50 of a HUD 1A. Also, FIG. 6B isa perspective view that shows the HUD 1A shown in FIG. 6A in state ofbeing disassembled into its components.

As shown in FIG. 6A and FIG. 6B, similarly to the HUD 1 according to thefirst embodiment, the HUD 1A has such configuration that the opticalcomponent holding member 53 is accommodated in the exterior case 54, andthe upper part is covered by the exterior lid section 51. Also, aself-luminous film irradiation device 100 is attached to an aperture ofthe exterior case 54 instead of the image display device 30 of the firstembodiment.

FIG. 7A is a perspective view that shows an example of an externalappearance of the self-luminous film irradiation device 100 according tothe second embodiment. FIG. 7B is a perspective view that shows theself-luminous film irradiation device 100 according to the secondembodiment in state of being disassembled into its components.

As shown in FIG. 7A and FIG. 7B, the self-luminous film irradiationdevice 100 includes a self-luminous film irradiation device housing(will be hereinafter abbreviated as “housing”) 102 and a projector 104.Also, the self-luminous film irradiation device 100 is configured todispose, on the optical path of the image light including the imageinformation irradiated from the projector 104 in order from theprojector 104 side, a first self-luminous film 110 that reacts to lightof a first frequency and emits first image light and a firstself-luminous film holder 111 that holds the first self-luminous film110, a second self-luminous film 112 that reacts to light of a secondfrequency and emits second image light and a second self-luminous filmholder 113 that holds the second self-luminous film 112, a thirdself-luminous film 114 that reacts to light of a third frequency andemits third image light and a third self-luminous film holder 115 thatholds the third self-luminous film 114, and a black screen 116 and ascreen holder 117 that holds the black screen 116.

The housing 102 includes a projector storage section 102 a thataccommodates the projector 104, a middle plate 102 c that includes anaperture 102 b through which the image light of the projector 104transmits, the projector 104 being accommodate in the projector storagesection 102 a, a side plate 102 d that covers one side surface of theprojector storage section 102 a and is erected toward the opposite sideof the projector storage section 102 a with reference to the middleplate 102 c, and a ceiling plate 102 e that is connected to an end onthe opposite side of the projector storage section 102 a in the sideplate 102 d and faces the middle plate 102 c. In the ceiling plate 102e, three slits 102 f, 102 g, 102 h are arranged at intervals along thetraveling direction of the image light. When each of the firstself-luminous film holder 111, the second self-luminous film holder 113,and the third self-luminous film holder 115 are inserted to each slit102 f, 102 g, 102 h, the first self-luminous film holder 111, the secondself-luminous film holder 113, and the third self-luminous film holder115 are held at intervals. To which of the slits 102 f, 102 g, 102 heach of the first self-luminous film holder 111, the secondself-luminous film holder 113, and the third self-luminous film holder115 is to be inserted may be changed appropriately. When the firstself-luminous film holder 111, the second self-luminous film holder 113,and the third self-luminous film holder 115 are inserted to each slit102 f, 102 g, 102 h and the projector 104 is stored in the projectorstorage section 102 a, the first self-luminous film 110, the secondself-luminous film 112, and the third self-luminous film 114 aredisposed within the irradiation range of the image light irradiated fromthe projector 104, and each of the first self-luminous film 110, thesecond self-luminous film 112, and the third self-luminous film 114receives the image light of the first frequency, the second frequency,and the third frequency and emits light.

The first frequency, the second frequency, and the third frequencydescribed above may correspond to each color of R, G, B for example.

The image light emitted from the projector 104 transmits the aperture102 b, and reaches the first self-luminous film 110, the secondself-luminous film 112, and the third self-luminous film 114. When imagelight included in the emitted image light reaches the firstself-luminous film 110, the first self-luminous film 110 reacts to thefirst frequency component out of the image light, and emits firstfrequency image light that includes image information of the firstfrequency component. In a similar manner, when the image light reachesthe second self-luminous film 112 and the third self-luminous film 114,each of the second self-luminous film 112 and the third self-luminousfilm 114 reacts to each of the second frequency component and the thirdfrequency component out of the image light, and emits second frequencyimage light that includes image information of the second frequencycomponent and third frequency image light that includes imageinformation of the third frequency component.

FIG. 8 is a drawing that shows the virtual image distance difference inthe second embodiment. As shown in FIG. 8, each of the first frequencyimage light, the second frequency image light, and the third frequencyimage light is made to be incident on the lens unit 43. Here, the firstoptical path length L1 of the first frequency image light is thedistance from the first self-luminous film 110 to the lens unit 43. In asimilar manner, the second optical path length L2 of the secondfrequency image light is the distance from the second self-luminous film112 to the lens unit 43. Also, the third optical path length L3 of thethird frequency image light is the distance from the third self-luminousfilm 114 to the lens unit 43. The optical path length difference ΔL1between the first optical path length L1 and the second optical pathlength L2 and the optical path length difference ΔL2 between the secondoptical path length L2 and the third optical path length L3 occur fromthe interval between the adjacent slits 102 f, 102 g, and 102 h.Further, although FIG. 8 illustrates an example where the slit intervalsare arranged generally equally and the optical path length differenceΔL1 and the optical path length difference ΔL2 are generally equal, itis also possible to differentiate the interval of the slits 102 f and102 g and the interval of the slits 102 g and 102 h and to differentiatethe optical path length difference ΔL1 and the optical path lengthdifference ΔL2.

When the formulas (2), (3), and (4) described above are applied to theexample of FIG. 8, a first virtual image (a red color image for example)by the first frequency image light, a second virtual image (a greencolor image for example) by the second frequency image light, and athird virtual image (a blue color image for example) by the thirdfrequency image light are displayed with the virtual image distancedifference obtained by multiplying the square of the magnification ofthe lens unit 43 to each of the optical path length differences ΔL1 andΔL2. Therefore, as seen from the driver 5, the first virtual image isdisplayed closest, the second virtual image is displayed in the middle,and the third virtual image is displayed farthest.

According to the present embodiment, the virtual images having differentvirtual image distance differences can be displayed similarly to thefirst embodiment.

Further, in the first embodiment, although the optical path lengthdifference is formed by holding the emission surface 33 a with thetilting attitude of being inclined by the tilting angle θ, in order tosecure contrast of the image quality, the range where the tilting angleθ can be obtained is limited. Meanwhile, in the present embodiment,because the optical path length difference of the first optical pathlength L1, the second optical path length L2, and the third optical pathlength L3 is formed by the interval of the slits 102 f, 102 g, and 102 harranged in the housing 102 of the self-luminous film irradiation device100, when the slit interval is enlarged, a larger optical path lengthdifference can be formed, and a virtual image distance difference largerthan that of the first embodiment can be achieved.

Third Embodiment

The third embodiment is an embodiment in which a folding mirror isdisposed between the image display device and the lens unit. A firstoptical path that is parallel to the lens optical axis and a secondoptical path image which is reflected by the folding mirror to divertthe image light and then enter the lens unit are formed. The secondoptical path is an optical path longer than the first optical path, andan optical path length difference occurs between the first optical pathand the second optical path. In the present embodiment, virtual imageshaving a virtual image distance difference are displayed using thisoptical path length difference.

FIG. 9A is a perspective view that shows an example of an externalappearance around the exterior housing 50 of a HUD 1B. Also, FIG. 9B isa perspective view of the HUD 1A shown in FIG. 9A being disassembledinto its components.

As shown in FIG. 9A and FIG. 9B, similarly to the HUD 1 according to thefirst embodiment, the HUD 1B has such configuration that the opticalcomponent holding member 53 is accommodated in the exterior case 54, andthe upper part is covered by the exterior lid section 51. Also, theimage display device 30 of the first embodiment is attached to anaperture of the exterior case 54 through a virtual image distancevariable mechanism 200.

FIG. 10A is a perspective view that shows an example of an externalappearance of the virtual image distance variable mechanism 200. FIG.10B is a perspective view that shows the virtual image distance variablemechanism 200 being disassembled into its components.

As shown in FIG. 10A and FIG. 10B, the virtual image distance variablemechanism 200 includes a virtual image distance variable mechanismhousing 210, and includes, in the virtual image distance variablemechanism housing 210, a first folding mirror 201 and a first foldingmirror holding section 201 h that is a holding member of the firstfolding mirror 201, the first folding mirror 201 being disposed on afirst optical path and reflecting image light towards a second opticalpath (detour optical path) different from the traveling direction of thefirst optical path, a first mirror drive section 203 that rotates thefirst folding mirror holding section 201 h for inserting or retractingthe mirror surface of the first folding mirror 201 to/from the firstoptical path, a first intermediate folding mirror 205 disposed on thesecond optical path and changing the traveling direction of thereflection light from the first folding mirror 201, a secondintermediate folding mirror 206 further reflecting reflection light fromthe first intermediate folding mirror 205, a second folding mirror 202and a second folding mirror holding section 202 h that is a holdingmember of the second folding mirror 202, the second folding mirror 202being disposed on the first optical path and reflecting reflection lightfrom the second intermediate folding mirror 206 along the travelingdirection of the first optical path, and a second mirror drive section204 that rotates the second folding mirror holding section 202 h forinserting or retracting the mirror surface of the second folding mirror202 to/from the first optical path.

Further, between the first intermediate folding mirror 205 and thesecond intermediate folding mirror 206, an optical lens (relay lens) 207is disposed. Also, each of the first mirror drive section 203 and thesecond mirror drive section 204 is connected to a controller 220(equivalent to a mirror control section) that outputs a mirror drivesignal (including an insertion signal and a retraction signal) forrotating the first folding mirror holding section 201 h and the secondfolding mirror holding section 202 h (refer to FIG. 12A).

In the present embodiment, the mirror surface of the first foldingmirror 201 faces the axis of the traveling direction of the image lightemitted from the display element 33 of the image display device 30 witha tilting angle in a state of being inserted onto the first opticalpath. Also, the mirror surface of the second folding mirror 202 facesthe axis of the traveling direction of the image light emitted from thedisplay element 33 of the image display device 30 with a tilting anglefor reflecting the image light toward the optical axis of the lens unit43 in a state of being inserted onto the first optical path.

Operation of the HUD 1B according to the present embodiment will beexplained referring to FIG. 11, FIG. 12A, FIG. 12B, and FIG. 12C. Eachof the first mirror drive section 203, the second mirror drive section204, and the image display device 30 is connected to the controller 220.The controller 220 executes control of a generation process of imageinformation executed by the image display device 30, and executes drivecontrol with respect to the first mirror drive section 203 and thesecond mirror drive section 204 according to the generated imageinformation.

FIG. 11 is a flowchart that shows a flow of an optical path switchingprocess executed by the controller 220.

The image display device 30 generates image information that isdisplayed as a virtual image (S1101), and displays the image informationon the display element 33. Irradiation light from the LED light source31 a transmits the display element 33, and the image light is emittedfrom the emission surface 33 a (S1102).

The controller 220 acquires the image information generated by the imagedisplay device 30 (S1103), and determines whether the virtual imagebased on the image information is to be displayed at a short distance ora long distance (S1104).

When the controller 220 determines to display at a short distance(S1104/short distance), a first optical path forming process isexecuted, that is, a retraction signal for moving the mirror surface ofthe first folding mirror 201 to a position for retracting from the firstoptical path is outputted to the first mirror drive section 203, and aretraction signal for moving the mirror surface of the second foldingmirror 202 to a position for retracting from the first optical path isoutputted to the second mirror drive section 204 (S1105).

FIG. 12A shows a state where the first optical path has been formed. Thefirst optical path is an optical path along which the image light havingtraveled straight is incident on the lens unit 43. At this time, byturning down the mirror surface of each of the first folding mirror 201and the second folding mirror 202 with respect to the first opticalpath, the mirror surfaces retract from the first optical path.

When the controller 220 determines to display at a long distance(S1104/long distance), a second optical path forming process isexecuted, that is, an insertion signal for inserting the mirror surfaceof the first folding mirror 201 onto the first optical path is outputtedto the first mirror drive section 203, and an insertion signal fordisposing the mirror surface of the second folding mirror 202 onto thefirst optical path and forming the second optical path is outputted tothe second mirror drive section 204 (S1106).

FIG. 12B is a drawing that shows a state where the second optical pathhas been formed. When the image light traveling the second optical pathreaches the first folding mirror 201, the image light is reflectedtowards the first intermediate folding mirror 205 by the first foldingmirror 201. The image light having reached the first intermediatefolding mirror 205 is further reflected, passes through the optical lens207, and reaches the second intermediate folding mirror 206.Furthermore, the image light is reflected towards the second foldingmirror 202 by the second intermediate folding mirror 206. The imagelight reflected by the second folding mirror 202 is incident from theaperture of the exterior case 54, and reaches the lens unit 43.

When the main switch of the HUD 1B is not turned off (S1107/No), theprocess returns to step S1101 to continue the virtual image distancecontrol process.

When the main switch of the HUD 1B is turned off (S1107/Yes), image asunlight blocking processing is performed to prevent sunlight fromentering the image display device 30 (S1108).

FIG. 12C shows a disposal state of each mirror in a sunlight blockingstate. In the sunlight blocking state, the controller 220 retracts themirror surface of the first folding mirror 201 from the first opticalpath, and inserts the mirror surface of the second folding mirror 202onto the first optical path. Thereby, the sunlight incident on the HUD1B is emitted from the lens unit 43 and reaches the second foldingmirror 202, it is reflected here and its is reflected by the secondintermediate folding mirror 206. Also, the sunlight that passes throughthe optical lens 207 is reflected by the first intermediate foldingmirror 205 and reaches the mirror surface of the first folding mirror201 which has been turned down with respect to the first optical path,and is reflected towards the first intermediate folding mirror 205. As aresult, the sunlight which has entered the HUD 1B is folded back by themirror surface of the first folding mirror 201 having been turned downwith respect to the first optical path, and therefore the sunlight canbe prevented from entering the image display device 30.

When the formations (2), (3), and (4) described above are applied to thepresent embodiment, a virtual image by an image having passed throughthe first optical path can be displayed closer and a virtual image by animage having passed through the second optical path can be displayedfarther with the virtual image distance difference obtained bymultiplying the square of the magnification of the lens unit 43 to theoptical path length difference ΔL between the first optical path and thesecond optical path.

The configuration of the controller 220 will be explained referring toFIG. 13A and FIG. 13B. FIG. 13A and FIG. 13B are drawings that show anexample of a functional block diagram of the controller.

In the example of FIG. 13A, an image information generation section 301that generates image information within the image display device 30 isincluded in the controller 220. Meanwhile, the controller 220 includesan image information acquisition section 2201 that acquires the imageinformation generated by the image information generation section 301, avirtual image distance determination information storage section 2202storing virtual image distance determination information that relatesthe image kind and the virtual image distance (either a short distanceor a long distance) at the time of displaying the image as a virtualimage, a virtual image distance determination section 2203 thatdetermines whether image information obtained from the image informationacquisition section 2201 is an image that becomes an object of shortdistance display or an image that becomes an object of long distancedisplay based on the virtual image distance determination information,and an optical path switching control section 2204 that outputs a mirrordrive signal for switching to the first optical path in executing shortdistance display, to the second optical path in executing long distancedisplay, and to a sunlight blocking state at the time of being turnedoff based on the determination result to each of the first mirror drivesection 203 and the second mirror drive section 204.

In the example of FIG. 13B, the image display device 30 includes thevirtual image distance determination section 2203 that acquires imageinformation from the image information generation section 301, refers tothe virtual image distance determination information stored in thevirtual image distance determination information storage section 2202that stores the virtual image distance determination information, anddetermines whether the image information generated is an image thatbecomes an object of short distance display or an image that becomes anobject of long distance display. Meanwhile, it may be configured thatthe controller 220 is provided with the optical path switching controlsection 2204, acquires determination information including thedetermination result of the virtual image distance determination section2203 from the image display device 30, and outputs a mirror drive signalfor switching to the first optical path, the second optical path, or thesunlight blocking state based on the determination information to eachof the first mirror drive section 203 and the second mirror drivesection 204. The operation flow of the present example mainly differsfrom the flow of FIG. 111 in that, instead that the controller 220acquires the image information from the image display device 30 in S1103of FIG. 11 and the processes of S1104 and onward are started, processesof S1103 to S1104 are executed within the image display device 30 andthe process of S1105 and onward are executed after the virtual imagedistance determination result information by S1104 is outputted to thecontroller 220.

FIG. 14 is a drawing that shows a hardware configuration example of thecontroller 220. The controller 220 includes a CPU (Central ProcessingUnit) 251, a RAM (Random Access Memory) 252, a ROM (Read Only Memory)253, an HDD (Hard Disk Drive) 254, and an I/F 255, and is configured byconnecting them to each other through a bus 256. The I/F 255 isconnected to the image display device 30, the first mirror drive section203, and the second mirror drive section 204, the image information orthe virtual image distance determination result information is inputtedto the controller 220, and the mirror drive signal is outputted.

The configuration corresponding to each functional block shown in FIG.13A and FIG. 13B may be configured by co-working of hardware and aprogram, the hardware configuring the image display device 30 and thecontroller 220 shown in FIG. 14, the program achieving the function ofeach functional block.

The present invention is not limited to the embodiments described above,and it is needless to mention that the present invention can be changedvariously within a range not departing from the gist of the presentinvention. For example, the embodiments described above were explainedin detail for easy understanding of the present invention, and are notnecessarily limited to those including all configurations explained.Also, a part of a configuration of an embodiment can be replaced by aconfiguration of another embodiment, and a configuration of anembodiment can be added with a configuration of another embodiment.

Further, with respect to a part of a configuration of each embodiment,addition, deletion, and replacement of other configurations arepossible.

REFERENCE SIGNS LIST

-   1, 1A, 1B . . . HUD-   2 . . . Vehicle-   3 . . . Windshield-   5 . . . Driver-   30 . . . Picture display device-   31 a . . . LED light source-   31 b . . . Heat sink-   32 . . . Illumination optical system-   32 a . . . Light funnel-   32 b . . . Light guide body-   33 . . . Display element-   33 a . . . Emission surface-   32 c . . . Diffusion plate-   32 d . . . Joining section-   33 . . . Display element-   34 . . . Flexible cable-   35 . . . Frame-   36 a, 36 b . . . Exterior member-   41 . . . Free curved surface mirror-   42 . . . Mirror drive section-   43 . . . Lens unit-   50 . . . Exterior housing-   51 . . . Exterior lid section-   52 . . . Glare trap-   53 . . . Optical component holding member-   54 . . . Exterior case-   55 . . . Optical component holding exterior case-   70 . . . Main base plate-   80 . . . Virtual image-   100 . . . Self-luminous film irradiation device-   102 . . . Housing-   102 a . . . Projector storage section-   102 b . . . Aperture-   102 c . . . Middle plate-   102 d . . . Side plate-   102 e . . . Ceiling plate-   102 f, 102 g, 102 h . . . Slit-   104 . . . Projector-   110 . . . First self-luminous film-   111 . . . First self-luminous film holder-   112 . . . Second self-luminous film-   113 . . . Second self-luminous film holder-   114 . . . Third self-luminous film-   115 . . . Third self-luminous film holder-   116 . . . Black screen-   117 . . . Screen holder-   200 . . . Virtual image distance variable mechanism-   201 . . . First folding mirror-   201 h . . . First folding mirror holding section-   202 . . . Second folding mirror-   202 h . . . Second folding mirror holding section-   203 . . . First mirror drive section-   204 . . . Second mirror drive section-   205 . . . First intermediate folding mirror-   206 . . . Second intermediate folding mirror-   207 . . . Optical lens-   210 . . . Virtual image distance variable mechanism housing-   220 . . . Controller-   251 . . . CPU-   252 . . . RAM-   253 . . . ROM-   254 . . . HDD-   255 . . . I/F-   256 . . . Bus-   301 . . . Picture information generation section-   2201 . . . Picture information acquisition section-   2202 . . . Virtual image distance determination information storage    section-   2203 . . . Virtual image distance determination section-   2204 . . . Optical path switching control section

1. A head-up display device displaying a virtual image for a driver,comprising: an image display device that emits image light; a virtualimage optical system that displays an image included in the image lightas a virtual image in front of a vehicle by reflecting the image lightemitted from the image display device by a projection target member; ahousing that stores the virtual image optical system; and a virtualimage distance variable mechanism that is disposed between the imagedisplay device and the virtual image optical system and forms a firstoptical path and a second optical path, the image light emitted from theimage display device being made to be incident on the virtual imageoptical system in the first optical path, the second optical path beinglonger than the first optical path, wherein the virtual image opticalsystem includes a lens unit and a free curved surface mirror disposedalong the emission direction of the image light in this order from aposition close to the virtual image distance variable mechanism, thevirtual image distance variable mechanism includes: a first foldingmirror that reflects the image light traveling along the first opticalpath toward the second optical path; at least one intermediate foldingmirror that changes the traveling direction of reflection light from thefirst folding mirror; a second folding mirror that reflects reflectionlight from the intermediate folding mirror so as to follow the travelingdirection of the first optical path; a first mirror drive section thatinserts or retracts a mirror surface of the first folding mirror to/fromthe first optical path; a second mirror drive section that inserts orretracts a mirror surface of the second folding mirror to/from the firstoptical path; and a mirror control section that controls drive of thefirst mirror drive section and the second mirror drive section, themirror control section outputs a retraction signal for retracting amirror surface of the first folding mirror from the first optical pathto the first mirror drive section and outputs a retraction signal forretracting a mirror surface of the second folding mirror from the firstoptical path to the second mirror drive section at the time of formingthe first optical path, and outputs an insertion signal for inserting amirror surface of the first folding mirror to the first optical path tothe first mirror drive section and outputs an insertion signal forinserting a mirror surface of the second folding mirror to the firstoptical path to the second mirror drive section at the time of formingthe second optical path, and the lens unit has an optical characteristicof optically enlarging an optical path length difference that is thedifference between an optical path length of the first optical path andan optical path length of the second optical path.
 2. The head-updisplay device according to claim 1, wherein the mirror control sectionexecutes optical path blocking control of controlling the first mirrordrive section or the second mirror drive section with respect to atleast one of the first folding mirror or the second folding mirror inorder to block both of the first optical path and the second opticalpath.
 3. The head-up display device according to claim 2, wherein themirror control section executes the optical path blocking control when amain switch has been turned off.